- Write a java program to accept a variable x. x can be any number from 1 to 230-1.
- Generate a file with x number of lines and each line consist of a string that is unique with 100 characters long
- Limitation: This java program needs to run with only 10M of ram.
- Requirement:
- You’re working in a team.
- Give us the program in GitHub public repo.
- The code has "separation of concern"
- The code is testable with Junit test
- The test coverage just need to be "enough"
- Scanner class will be used to take user input as String.
- If user write "END", this program will close.
- System will validate String can be parsed to int.
- If failed, then will show validation message.
- If passed, will go to next step.
- System will check valid input for Null / Empty / Blank.
- System will validate String can be parsed to int.
- System will validate against minimum & maximum accepted range.
- System will generate file out put path "\src\main\resources" and name "uvTech.txt".
- System will validate if number is zero and/or the path is null or not.
- Since the max acceptable value is (2^30 - 1 ), that is equal to 1073741823, here we will do the following approach.
- Instead of iterating for each line , we will iterate using the following.
- Number of Iteration = input number / 4;
- For each iteration, we will write to the destination file.
- This will reduce the number of write operation.
- So, why we take 4 ?
- Here, we will generate one string of 100 length using byte[].
- And put this byte[] to ByteBuffer that is 4 times in size of this byte[]
- Above will be itrate for 4 times. What it means that the write operations are done in small chunks.
- And, the ByteBuffer's is cleared so that this can be used for next iteration.
- Then, the ByteBuffer will be write to file that is being opened previously.
- For file operations, we are using FileChannel & FileOutputStream. These, are invoked inside the try resources.
- We created the required unit test code. We runned and observed the following.
- For max accpeted number,
- the file size is huge (more than 100 GB).
- the memory used : 5+ MB
- the time elapsed : 18 mins(+/-).
- Measurement Formula:
- At the beginning:
- runtime = Runtime.getRuntime()
- startTime = System.nanoTime();
- Upon successful file generation:
- memory = runtime.totalMemory() - runtime.freeMemory()
- timeElapsed = endTime - startTime
- At the beginning:
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